The present invention relates generally to bar code readers and more particularly, to a power supply control circuit for allowing the reader system to receive full power only during the time the system is in a read mode. Present-day bar code reader systems include an optical wand for sensing the black and white bars which constitute the bar code, i.e., the bars forming coded binary data, the bar being printed on an article or a tag attached to the article to which the data pertains. The reader system further includes reader electronics for converting the signals generated by the optical wand in reading the bar code into digital data and for processing such data.
Present-day merchandise checkout systems include the use of bar code readers for reading data associated with merchandise items purchased by the customer, the data may include manufacturer number, merchandise number, etc. Normally the power supplied to the reader system is on during the time the checkout counter is available for operation. It has been found that during an average day of operation, the time the optical wand is actually in use in reading the coded labels or articles is a fraction of the time that the check-out counter is in operation. In view of the increased costs of electrical power, it is desirable to reduce the power consumption of the bar code reader system, thereby reducing its cost of operation and therefore enhancing its value to the proprietor.
At the present time, portable bar code reader systems are in existence which are battery powered. In order to conserve the life of the battery in such systems, circuits have been devised for limiting the power supply to the optical wand to the time the wand is actually sensing a label or article. Examples of this type of circuit may be found in U.S. Pat. No. 3,925,639 and U.S. Pat. No. 4,072,859. While these control circuits perform their intended task, they are complex and costly. It is therefore a principal object of this invention to provide an improved circuit for controlling the power supplied to a bar code reader system used in a merchandise check-out arrangement. It is a further object of this invention to provide such a circuit which is simple in its construction, and therefore, low in cost.